[Role of phosphate and divalent metal ions in regulation of the activity of the alpha-ketoglutarate dehydrogenase complex from adrenal cortex].
Studies of the alpha-ketoglutarate dehydrogenase complex have demonstrated that inorganic phosphate ions cause a decrease in the Km value for alpha-ketoglutarate without changing the maximum reaction rate. In the absence of phosphate (tris-HCl buffer) at low concentrations of alpha-ketoglutarate there are some indications of enzyme-substrate cooperative interactions (the Hill coefficient is 1,6). The cooperativity is removed by ADP, which increases the apparent affinity of the enzyme for alpha-ketoglutarate. Upon divalent cations binding to EDTA in the presence of high (20 mM) concentrations of alpha-ketoglutarate the reaction rate is decreased only by 20%, while the value of Km for the given substrate shows a sharp rise. The nature of Mg2+, Ca2+, Ba2+ and Mn2+ effects on the alpha-ketoglutarate dehydrogenase complex activity depends on their concentration.
D000302:Adrenal Cortex / Q000201:enzymology*; D000818:Animals; D002413:Cations, Divalent; D002417:Cattle; D004492:Edetic Acid / Q000494:pharmacology; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism*; D007658:Ketone Oxidoreductases / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010710:Phosphates / Q000494:pharmacology*
D002413:Cations, Divalent; D010710:Phosphates; D004492:Edetic Acid; D007658:Ketone Oxidoreductases; D007655:Ketoglutarate Dehydrogenase Complex
Rol' ionov fosfata i dvukhvalentnykh metallov v reguliatsii aktivnosti al'fa-ketoglutaratdegidrogenaznogo kompleksa kory nadpochechikov.